Power supply apparatus

ABSTRACT

A power supply apparatus is shown that comprises several identical individual power packs connected in parallel so as to be decoupled from one another. The individual power packs produce coupled output voltages, of which one is adjusted by a pulse duty control and the others are corrected in linear fashion. By means of a correction such that a comparison of target/actual output voltage values is done without, the mean value of all the actual current values is formed, and a mistuning of a respective target/actual current comparison is carried out, a constantly uniform current distribution to the individual power packs is achieved, with a low power loss, fault tolerance via possible redundancy, and the possibility of &#34;hot board replacement.&#34;

BACKGROUND OF THE INVENTION

The invention concerns a power supply apparatus with identicalindividual power packs connected in parallel and decoupled from oneanother, with outputs for coupled output voltages, of which one isrespectively adjusted by pulse duty control and the others are correctedby linear correction units.

Computer equipment or tower PCs with higher data processing powerrequire power supply apparatuses with higher power. As a higher-powerpower supply apparatus, power supply apparatuses consisting of severalidentical individual power packs are used. The individual power packsare connected in parallel, decoupled from one another. They can beconstructed in such a way that they produce coupled output voltages, ofwhich one is adjusted by means of a pulse duty control and the othersare adjusted by a linear correction. The linear correction is subject toa loss of power that is all the larger, the larger a derivative actionhas to be between an incoming voltage to be compensated and an outgoingcompensated voltage.

Besides the higher power, additionally increased demands are placed onthe fault tolerance of this power supply apparatus. A redundant powersupply apparatus is required that continues to supply the computer incase of failure of an individual power pack, without failure or collapseof system voltages.

An additional demand on the power supply apparatus is that a failedindividual power pack can be exchanged while the computer is runningwithout voltage collapse. This measure is also known by the term "hotboard replacement."

Finally, a uniform distribution of current to the individual power packsshould be ensured.

It is known to control the uniform distribution of the currentelectronically. It is also known to use a separate power pack circuitfor each output voltage. It is also known to decouple the outputs fromthe system voltage inputs of the computer with Schottky diodes, in orderto obtain a redundancy given an output short circuit of a defectiveindividual power pack. In addition, it is known to choose the number ofindividual power packs connected in parallel to be higher by one thanthe number actually required, in order to obtain in this way a powersupply apparatus with redundancy in which defective individual powerpacks can be exchanged during operation.

The possibility is also known of connecting individual power packs withcoupled output voltages in parallel. The output voltage with a highestoutput current is regulated for uniform current distribution via a pulseduty control. The coupled output(s) are regulated for a uniform currentdistribution by means of a transistor element as a controlling elementin an output line. The regulation of the current distribution canthereby respectively ensue in an identical fashion: a central controlblock compares each output voltage separately with a target value. Thedeviation from this target value is amplified and is used as targetcurrent of the respective output. The actual current is acquired, iscompared with the target value and is corrected correspondingly.

However, this method has the disadvantage that while the uniform currentdistribution of coupled individual power packs is indeed ensured, thelosses due to this type of control are higher than is absolutelynecessary. The reason for this is that an output voltage target value isused that is unalterably set, which value is not matched to the actuallypresent output voltages. A power supply apparatus as described above isknown from U.S. Pat. No. 5,038,265.

From DE 3 941 052 C1, a circuit arrangement for the parallel connectionof power supply units is known, said units comprising a voltageregulation apparatus and a current regulation apparatus operatingsecondarily thereto, which respectively have identical resistanceswitching networks, as mean value formation units, between the voltageregulation apparatus and the current regulation apparatus, for theprotection of a uniform load distribution to the power supply unitsconnected together in parallel to form a power supply packet, whichswitching networks are connected with one another via at least onebidirectional control line and calculate a common mean value of a signalfor all power supply units, which signal represents a measure for theoutput power to be emitted.

European reference 0 419 993, a power supply apparatus is known thatconsists of identical individual power packs decoupled from one anotherand connected in parallel, comprising outputs for coupled outputvoltages. With respect to each individual power pack, a pick-off circuitis provided for picking off a coupled output current, allocated to acontrolling element within a power pack, as an electrical actualquantity, which circuit comprises among other things a drain connectedwith threshold switches. Overall, a uniform distribution of current tothe individual power packs is effected by the formation of a targetvalue from the mean value of the measured currents. However, the powerpacks comprise no coupled output voltages such that one is respectivelyadjusted by a pulse duty control and the others are corrected by linearcorrection units with a linearly controllable controlling element and acomparator connected with it. The present power supply apparatus thusdoes not solve the problem of ensuring a correction with minimal powerloss and simultaneous uniform current distribution to the individualpower packs connected in parallel in power supply apparatuses of thissort.

The aim of the invention is to ensure a correction of output voltages ina power supply apparatus of the type named above, with a minimal powerloss and simultaneous uniform current distribution to the individualpower packs connected in parallel.

SUMMARY OF THE INVENTION

In the regulation of coupled outputs connected in parallel on whichthese features are based, a comparison of target value and actual valueof the output voltage in order to obtain a target current value is nolonger carried out. The target current value is obtained by forming themean value of all the actual current values.

Due to tolerances in the target/actual current comparators, these wouldeither respectively completely turn on the respective correctiontransistors that act as controlling elements or would shut them offentirely. In order nonetheless to bring the current distributionmechanism to functioning, a deliberate mistuning of the respectivetarget/actual current comparator is carried out by means of a drain. Inthis way, each correction transistor will turn on completely at thebeginning. In the individual power pack with the lowest output voltage,the current, and thereby the common target current value, will then sinkuntil the common target current value compensates the deliberatemistuning of the remaining target/actual current comparators. By thismeans, the remaining correction transistors come into the control range,and produce a uniform current distribution with a small deviation causedby the mistuning. This deviation can be disregarded given suitabledimensioning. Since the correction transistor with the lowest outputvoltage continues to remain completely switched on, the lowest possiblepower loss arises in all the individual power packs.

Since the correction addressed above ensures the lowest possibleresidual voltage over the correction transistors, the tasks of thedecoupling diodes and the correction transistors can be taken over by acommon component: by an n-channel MOSFET transistor whose drain diodepoints in the direction of the output current flow. The differencebetween the drain-diode residual voltage and the residual voltage of theturned-on correction transistor of about 0.5 volts then serves for thecorrection of tolerances in the output voltages of the individual powerpacks connected in parallel.

To produce the decoupling between the individual power packs, the MOSFETcorrection transistors can be arranged in such a way that their draindiodes are arranged opposite to the direction to the output of the powersupply apparatus, and that decoupling diodes are provided that arearranged in such a way that they are poled in the reverse direction inrelation to a reverse current. The same effect can also be produced byconnecting the MOSFET correction transistors in such a way that theirdrain diodes are arranged in the direction of the output of the powersupply apparatus. The decoupling diodes formerly required can then beomitted. In an individual power pack with an output short circuit, aproper MOSFET correction transistor must be actively switched off incase of a reverse current flow. For this purpose, only an additionaloperational amplifier is for example necessary. Nonetheless, thisalternative has the advantage that with the omission of the decouplingdiode, which for example has to be able to handle 5 A, for which acooling is required, the cooling is also omitted, including the assemblyit requires.

A possibility for the realization of the mistuning is given by a voltagedistributor, one of whose two resistances is used for the drain. Acircuit component equipped with a Zener diode would also be possible forthe drain.

A realization of the mistuning such that the mistuning is related to anegative auxiliary voltage has the advantage of control over thecritical situation in which no current at all is let through by theassociated individual power pack.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the present invention which are believed to be novel,are set forth with particularity in the appended claims. The invention,together with further objects and advantages, may best be understood byreference to the following description taken in conjunction with theaccompanying drawings, in the several Figures of which like referencenumerals identify like elements, and in which:

FIG. 1 shows a diagram of a parallel circuit of individual power packsdecoupled via diodes, with coupled output voltages, and

FIG. 2 shows a diagram of the current regulation according to theinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a power supply apparatus that comprises several identicalindividual power packs ENTa; ENTb; ENTc. The individual power packsENTa; ENTb; ENTc produce specific output voltages Uout1a, Uout2a;Uout1b, Uout2b; Uout1c, Uout2c, coupled to a ground GND. The outputvoltages Uout1a, Uout1b and Uout1c can be for example a 5 volt voltage,adjusted via a pulse duty control. The output voltages Uout2a, Uout2band Uout2c are for example a 12 volt voltage.

The individual power packs ENTa; ENTb; ENTc are connected in parallel atthe input side and are connected to an input network alternating voltageACin. At the output side, the individual power packs ENTa, ENTb, ENTcare likewise connected in parallel per output voltage produced. Theindividual power packs are parallelized in relation to the 5 volt outputvoltage via a parallel 5 volt bus line IBUS5V. A uniform currentdistribution to the individual power packs ENTa, ENTb, ENTc ensues viaacquisition of the 5 volt output current or primary input current, meanvalue formation via the 5 volt bus line IBUS5V and correction of theprimary pulse duty corresponding to the voltage at the 5 volt bus lineIBUS5V (compare the reference DE 3 941 052 C1, mentioned above). Adecoupling of the individual power packs in relation to the 5 voltoutput voltage is to be assumed within the boxes for the individualpower packs. It is not additionally shown for the 5 volt output voltagein FIG. 1. The 5 volt output voltage is smoothed to an output voltageUOUT1 of the power supply apparatus via an output capacitor C1.

The same holds analogously for the 12 volt output voltage of theindividual power packs ENTa, ENTb, ENTc, which is smoothed to an outputvoltage UOUT2 of the power supply apparatus via an output capacitor C2.The only difference is that the 12 volt output voltage is coupled to the5 volt output voltage. The exact adjustment takes place via a linearcorrection.

The 12 volt voltages of the individual power packs ENTa; ENTb; ENTc arerespectively corrected before the parallel circuit by means of linearcorrection units, as mentioned. The linear correction units comprisecontrolling elements Qa, Qb, Qc that can be controlled in linearfashion. The controlling elements Qa, Qb, Qc are connected in serieswith decoupling diodes Da, Db, Dc. The decoupling diodes Da, Db, Dc arepoled in the direction of the output of the power supply apparatus.

Each correction unit has a circuit part, shown as a box in FIG. 1, whoseinternal activity is shown in more detail in FIG. 2. Overall, thecircuit part, shown as a box, receives the output current to becorrected via a pick-off circuit. The supplying ensues via lines Ia, Ib,Ic. The picking off can for example ensue by means of a shuntresistance.

The controlling elements Qa, Qb, Qc are controlled from a respective boxvia lines Ga, Gb, Gc. A line IBUS connects the individual boxes of thecorrection units.

As an example, FIG. 2 shows in more detail the structure of the box fromFIG. 1 belonging to the individual power pack designated ENTa. Therepresentation can be carried over analogously to the boxes for theindividual power packs designated ENTb and ENTc in FIG. 1.

In the box shown in more detail, a comparator Va is shown that is wiredwith a compensation Comp for the removal of the oscillation tendency.The comparator Va can be an operational amplifier with a negative and apositive output. The compensation Comp is connected between the negativeoutput and the output of the comparator Va.

The output of the comparator Va is connected with the line Ga. Thenegative input of the comparator Va is connected to a negative voltagepotential via a resistance Ra. In the exemplary embodiment, the negativevoltage potential is -12 volts.

A drain Uoffseta is connected to the negative input of the comparatorVa. The connection ensues via one of the terminal sides of the drain.With the other terminal side, the drain Uoffseta is connected with aterminal side of a resistance component RSa and with the line Ia.

The other terminal side of the resistance component RSa is connectedwith a positive input of the comparator Va and with the line IBUS.

The drain Uoffseta can for example be formed by a resistance that formsa voltage divider together with the resistance Ra. However, the drainUoffseta could also be formed by a Zener diode and two resistances.

The comparator Va carries out a comparison of a target current with anactual current. The target current is present at the positive input andthe actual current is present at the negative input of the comparatorVa.

In order to avoid repetitions, with respect to the specification of themanner of functioning of the power supply apparatus indicated in FIGS. 1and 2, reference is made to the introductory part of the presentdocuments.

The invention is not limited to the particular details of the apparatusdepicted and other modifications and applications are contemplated.Certain other changes may be made in the above described apparatuswithout departing from the true spirit and scope of the invention hereininvolved. It is intended, therefore, that the subject matter in theabove depiction shall be interpreted as illustrative and not in alimiting sense.

What is claimed is:
 1. Power supply apparatus, having identicalindividual power packs decoupled from one another and connected inparallel, comprising:outputs for coupled output voltages of a respectiveindividual power pack, of which one output is respectively adjusted by apulse duty control and other outputs are corrected by linear correctionunits with a controlling element that is controllable in linear fashionand with a comparator connected with a control input of the controllingelement, which comparator compares an electrical target quantity with anelectrical actual quantity and correspondingly controls the controllingelement dependent on a result of the comparison; a pick-off circuitallocated before each linearly controllable controlling element forpicking off a coupled output current allocated to the controllingelement as an electrical actual quantity, which pick-off circuit is atconnected respectively with first terminal sides of a resistancecomponent and with a drain, of which the drain is connected, with asecond terminal side, with an input for an actual quantity of thecomparator, and the resistance component is connected, with a secondterminal side, with an input for a target quantity of the comparator,and the pick-off circuit connected with a bus line that is respectivelyconnected with the second terminal sides of the resistance components ofthe correction units of respective further individual power packs thatare connected in parallel, and thereby providing a target current valuethat is obtained by forming a mean value of all actual current values;and respectively allocated pick-off circuits having drains dimensionedsuch that a defined mistuning of a respective target/actual currentcomparison is effected.
 2. The power supply apparatus according to claim1, wherein the controlling elements are formed by MOSFET transistorswhose drain diode is arranged opposite to a direction to an output ofthe power supply apparatus, and wherein mutual decoupling of theindividual power packs are formed for each of the output voltagesidentical among themselves by decoupling diodes, which are poled in adirection of flow of current of a respectively associated outputcurrent, and which are connected together at an output side to form anoverall output for a resulting overall output voltage.
 3. The powersupply apparatus according to claim 1, wherein the controlling elementsare formed by MOSFET transistors whose drain diode is arranged in adirection to an output of the power supply apparatus, and wherein thecontrolling elements for each identical output voltage among theindividual power packs are connected together at an output side to forman overall output for a resulting overall output voltage.
 4. The powersupply according to claim 1, wherein the drain for a picked-offelectrical actual quantity is a resistance.
 5. The power supplyaccording to claim 1, wherein the drain for a picked-off electricalactual quantity is at least one Zener diode.
 6. The power supplyapparatus according to claim 1, wherein a redundancy is provided byadditionally providing an individual power pack in relation to apredetermined number of individual power packs.